1. Technical Field
The present invention relates to a focus detection device and an automatic focusing device for a camera.
2. Prior Art
Conventionally, an automatic-focusing camera of the kind as referred to above, is so arranged that an in-focus level is set to indicate that the objective lens is in an in-focus position with respect to the target object or an object to be photographed, while, through detection of the camera-to-object distance or the defocus state of an object image formed by an objective lens, with a range finding means or focus detecting means constituted by photosensitive elements, etc., the level of the detection signal for the camera-to-object distance or the defocus state of the object image is adapted to be relatively shifted in level with respect to the in-focus level, following the adjusting operation of the objective lens so that the objective lens is stopped when the detection signal has reached the in-focus level.
In the known arrangement as described above, however, there has been such a disadvantage that since detection signals from a distance measuring means or focus condition detecting means tend to be subjected to level variations consequent to disturbances or noise internally generated in the circuits, even after the objective lens has been stopped at the in-focus position, if the level of the detected signal is deviates from the in-focus level referred to earlier by such level variations, the objective lens resumes the reciprocating movement therewith, thus resulting in the inconvenience that the lens can not readily be stabilized at the predetermined in-focus position.